1. Field of the Invention
The present invention relates to a gate valve system that is capable of cutting an existing pipe with water flowing therethrough or the like therein without cutting off the water.
2. Discussion of the Background
In the following description, the terms, "lateral", "vertical" and "downward", as well as "downwardly", "laterally" and "vertically", or other terms indicating the directions, used herein are meant to indicate those directions as viewed in a front view as shown in FIG. 22, and based upon the longitudinal axis of the gate valve system installed on the existing pipe.
A well known method of cutting an existing pipe with water flowing therethrough includes boring the wall of an existing pipe without cutting off the water therein during forming a through-hole, and placing a gate valve into the pipe through the through-hole formed in the wall of the pipe. It is desirable to form the through-hole as smaller as possible, specifically the through-hole of a diameter smaller than the diameter of the pipe.
To form the through-hole of such a smaller diameter, the gate valve needs to be of such a construction as to be placed into the inside of the pipe via the through-hole having a diameter small than the diameter of the pipe, as well as to be capable of hermetically sealing the inside of the pipe for cutting off the water flowing therethrough. To accomplish these requirements, the gate valve includes a support member 61, and a seal member 63 supported on the support member 61, which exhibits an elastically deformable property for sealing the existing pipe 62.
The gate valve of the above type accomplishes the water cutting-off by forcing the support member 61 into the existing pipe having a circular cross section via the through hole of a diameter smaller than the diameter of the existing pipe 62 to allow the seal member 63 to hermetically contact the inner surface of the existing pipe 62.
However, the curved surface of the pipe may hesitate the seal member 63 from sufficiently expanding towards lateral sides of the pipe, and therefore pose a problem that a part of the peripheral edge portion of the seal member 63 cannot reach the inner surface of the pipe 62, and therefore a hermetic contact of the seal member 63 against the pipe 62 is hardly accomplished, which leads to a poor water tightness. To overcome this problem, some types of members for laterally expanding the seal member 63 were developed.
The means for laterally expanding the seal member 63 has such a construction that a plurality of seal expanding members are arranged inside of the support member 61 to mechanically expand the seal member 63. This may need a complicated structure and a relatively large size of the gate valve, which are disadvantageous for the existing pipe of a smaller diameter, and which also increase the manufacturing costs.
The present invention has been conceived in consideration of the above problem. It is an object of the present invention to provide a gate valve system that is of a simple construction and a smaller size.
It is another object of the present invention to provide a gate valve system that is capable of sufficiently cutting off the water flowing through the existing pipe.
It is still another object of the present invention to provide a gate valve system that can be manufactured in a cheap manner.